Garry Lockhart, 33, is accused of strangling his wife, Janet, and suffocating their son, Michael, at their home in Bonnyrigg, Midlothian, in December last year.
He pleaded not guilty to both charges of murder when he appeared at the High Court in Edinburgh today.
Prosecutors allege that he placed and held a pillow over Michael's face, put his hands over his nose and mouth, and by these means or "other means unknown" restricted his breathing and suffocated him.
Lockhart is also accused of assaulting his 29-year-old wife, placing his hands and arm around her neck, compressing her neck and strangling her on December 28.
Judge Lord Bannatyne set a continued hearing for August 18, with the case expected to go to trial in September.